Random Parameters and Sources of Uncertainty in Practical Fire Safety Assessment of Steel Building Structures

The purpose of this article is to identify sources of uncertaintyand outline the basis of probabilistic safety assessmentof steel structures exposed to fire conditions. Awareness of theexistence of unavoidable uncertainties and non-deterministicnature of many phenomena and parameters may be essentialfor a proper understanding of the issues of structural reliabilityin the event of extreme or accidental actions.The study highlights various sources of uncertainty associatedwith practical fire safety assessment of steel structureswhich significantly affects the reliability of estimates. Universalfactors influencing random structural resistance in alldesign conditions were separately described. A significant partof the paper is devoted to issues that relate only to an accidentaldesign situation of fire. Reference was made to the uncertaintyof the analytical model describing the bearing capacityof the structure in terms of probabilistic approach. A syntheticsummary on the impact of the method of carrying out materialtesting in elevated temperatures on the strength parameters,was made. In the conclusion it has been underlined that, interalia, due to the lack of relevant statistical data, conducting afully reliable probabilistic analysis of random structural resistanceunder fire is currently not possible. A unique part of thepaper contains the proposed model of probability-based analyticalapproach to assess random structural resistance in fireconditions, incorporating an authorial modification to modelsused for standard conditions.